Here are my two favorite chess checkmate-in-one-move positions. Checkmate in one move? How hard can it be? All you have to do is try every possible move, right? Maybe. White to move.
The first position is an artificial composition by Leonid Hubbel. The position could not have occurred in a real game, but there’s no trick — it’s just very hard to find the one move that delivers checkmate. Many moves that appear to work, just don’t because black can block or the move is illegal (for example d8=Q isn’t legal because it would expose the white King to check). I count approximately 78 possible White moves to consider.
The second position is somewhat of a trick. The only way to find the solution is if you know that in fact there is exactly one move that does deliver checkmate.